Gateway to route communications during a fault

ABSTRACT

Telephones connected to a gateway can still make calls when connectivity to a central processing device is lost. The gateway determines when connectivity with the central processing device is lost. When a communication is received from a first telephone for second telephone, the communication is routed to the second entity by bypassing the central processing device. This is possible using identification information that is stored for the second entity when the second entity registered with the central processing device.

BACKGROUND OF THE INVENTION

Embodiments of the present invention generally relate totelecommunications and more specifically to techniques for rerouting ofcommunications when connectivity to a central communication processor islost.

A central office exchange service (Centrex) is a service offered bylocal telephone companies in which phone facilities at the phonecompanies' central (local) office are offered to users. For example, theCentrex service allows centralized services to be provided for businesscompanies. The Centrex services may be similar to those provided by aprivate branch exchange (PBX) service, which is owned by a businessentity, and provides services to users in the business entity. TheCentrex, which may be referred to by different names in differentlocations, provides users in a business entity with as much if not morecontrol over the services that are offered by a PBX system.

Calls from a user of the business entity are typically routed throughthe Centrex. In a Voice over IP network using SIP, these calls typicallyare routed through a wide area network (WAN) that is external to thebusiness entity. For example, the wide area network may include anetwork from a business office to another location, such as a centraloffice or another office. The wide area network may be unreliable andconnectivity may be lost with the Centrex. Further, the Centrex may notbe functioning or may crash. If connectivity to the Centrex is lost,then the users of the business entity may not be able to communicatewith other users. For example, a user may not be able to make atelephone call to any other users because the telephone call needs to berouted to the Centrex in order to be routed to its destination. Thus,even calls to users in the same office building cannot be made.Accordingly, the business entity will experience downtime for thetelephone system if connectivity to the Centrex is lost.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention generally relate to techniques forrerouting communications when connectivity to a central communicationprocessor is lost.

In one embodiment, telephones connected to a gateway can still makecalls when connectivity to a central processing device is lost. Thegateway determines when connectivity with the central processing deviceis lost. When a communication is received from a first telephone forsecond telephone, the communication is routed to the second entity bybypassing the central processing device. This is possible usingidentification information that is stored for the second entity when thesecond entity registered with the central processing device.

In one embodiment, a method for providing routing of calls whenconnectivity with a central processing device is lost is provided. Themethod includes: receiving one or more registration requests from one ormore entities; sending the one or more registration requests to thecentral processing device; receiving confirmation that the one or moreregistration requests have registered the one or more entities with thecentral processing device; storing information for the one or moreentities at the gateway in response to the one or more registrationrequests, the information including identification information for theone or more entities; determining that the connectivity with the centralprocessing device is lost; receiving a communication from a first entityin the one or more entities for second entity in the one or moreentities; and routing the communication to the second entity using theidentification information stored for the second entity wherein thecommunication bypasses the central processing device.

In another embodiment, a gateway configured to provide routing of callswhen connectivity with a central processing device is lost is provided.The gateway comprises: logic configured to receive one or moreregistration requests from one or more entities; logic configured tosend the one or more registration requests to the central processingdevice; logic configured to receive confirmation that the one or moreregistration requests have registered the one or more entities with thecentral processing device; logic configured to store information for theone or more entities at the gateway in response to the one or moreregistration requests, the information including identificationinformation for the one or more entities; logic configured to determinethat the connectivity with the central processing device is lost; logicconfigured to receive a communication from a first entity in the one ormore entities for second entity in the one or more entities; and logicconfigured to route the communication to the second entity using theidentification information stored for the second entity wherein thecommunication bypasses the central processing device.

In another embodiment, a system configured to provide routing of callswhen connectivity with a central processing device is lost is provided.The system comprises: a plurality of communication devices; a centralprocessing device configured to process a communication from a firstcommunication device to a second communication device in the pluralityof communication devices; and a gateway comprising: logic configured toreceive registration requests from first and second communicationdevices; logic configured to send the registration requests to thecentral processing device; logic configured to receive confirmation thatthe registration requests have registered the first and secondcommunication devices with the central processing device; logicconfigured to store information for the first and second communicationdevices at the gateway in response to the one or more registrationrequests, the information including identification information for thefirst and second communication devices; logic configured to determinethat the connectivity with the central processing device is lost; logicconfigured to receive a communication from the first communicationdevice for the second communication device; and logic configured toroute the communication to the second entity using the identificationinformation stored for the second entity wherein the communicationbypasses the central processing device.

A further understanding of the nature and the advantages of theinventions disclosed herein may be realized by reference of theremaining portions of the specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a system according to one embodiment of the presentinvention.

FIG. 2 depicts a gateway according to embodiments of the presentinvention.

FIG. 3 depicts a message below for registering with a central processingdevice using a telephone according to one embodiment of the presentinvention.

FIG. 4 shows the message flow for routing communications between a firsttelephone and a second telephone according to one embodiment of thepresent invention.

FIG. 5 depicts a more detailed block diagram of the gateway for handlingcommunications when connectivity with the central processing device islost according to one embodiment of the present invention.

FIG. 6 depicts a message flow when connectivity is lost with the centralprocessing device according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a system 100 according to one embodiment of the presentinvention.

As shown, system 100 includes one or more local areas 101, a wide areanetwork (WAN) 110, and a central area 114. Local areas 101 may include agateway 102, a local area network (LAN) 104, and one or more telephones106. Central area 114 may include a central processing device 112.

Local area 101 may include any number of telephones 106. In oneembodiment, local area 101 may be a branch office for a business. Forexample, a business may have multiple branch offices 101-1, 101-2, and101-3. In one example, a business may have offices in San Francisco, LosAngeles, and New York. Also, local areas 101 may be divided in any otherways, such as by floors, sections of floors, etc.

A local area 101 includes a gateway 102. Gateway 102 is configured totransfer communications from telephones 106 to central processing device112. In one embodiment, when a connection request is received from atelephone 106 for another telephone 106, the request goes throughgateway 102, which transfers the request to central processing device112. Gateway 102 may be at the border of local area 101. In oneembodiment, communications from telephones 106 found in local area 101go through gateway 102 for routing.

Local area network 104 may be any network found in area 101. In oneembodiment, a local area network is a group of computers and associateddevices that share a common communications line or a wireless linkwithin a small geographic area. The LAN may serve as few as two or threeusers (such as in a home network) or as many as thousands of users (forexample, as in a fiber distributed data interface (FDDI)).

Telephones 106 may include any devices configured to send communicationsto gateway 102. For example, telephones 106 include cellular phones,telephones, personal computers, personal digital assistants (PDAs),personal PCs, blackberry devices, GoodLink devices, softphones, VoIPtelephones, instant message clients, etc. In one embodiment, telephones106 are configured to communicate using a SIP protocol. In otherembodiments, telephones 106 may communicate using a non-SIP protocol.

Wide area network (WAN) 110 includes any network that can routecommunications from gateway 102 to central processing device 112. In oneembodiment, a wide area network is a geographically disbursedtelecommunications network. Wide area network 110 may be defined as anetwork that is outside of local areas 101 and may be shared by multiplelocal areas 101 or local area networks (customer networks). For example,WAN 110 may include privately owned or rented networks and/or public(shared user) networks. One example of a WAN is a metropolitan areanetwork (MAN).

Central area 114 includes any area from which a central point incommunications is provided. For example, local area 101-1, local area101-2, and local area 101-3 send communications through central area 114to other destinations. In one embodiment, central area 114 includes acentral office that is operated by a local telephone company.

In one embodiment, central processing device 112 may be a Centrex. TheCentrex may be any central processing device configured to processcommunications from local areas 101. The Centrex provides a service thatallows centralized services to be provided for business companies. TheCentrex services may be similar to those provided by a private branchexchange (PBX) service, which is owned by a business entity. TheCentrex, which may be referred to by different names and differentlocations, provides users in a business entity with as much, if notmore, control as the services offered by a PBX system. Although aCentrex is described, it will be understood that any centralized devicethat provides routing of communications may be used.

In one embodiment, central communications device 112 is configured toroute calls using the SIP protocol. However, it will be understood thatcentral processing device 112 may use other protocols to routecommunications. Central processing device 112 can also authenticate theusers of the registrations and also callers to ensure that the calls arecoming from authorized users. It can use information such as usernamesand passwords to perform the authentication.

FIG. 2 depicts a more detailed embodiment of gateway 102 according toembodiments of the present invention. As shown, gateway 102 includes acommunicator 202 and storage device 204.

Telephone 106 sends a register request. The register request is anyrequest that registers telephone 106 with central processing device 112.For example, the register request may provide information for telephone106, such as contact information, or indicate that telephone 106 isactive and can receive communications. When telephones 106 are booted upor turned on, they may all register with central processing device 112.

Communicator 202 is configured to receive the register request andforward it to central processing device 112. In one embodiment,telephones 106 in a local area 101 have private identifiers, such asprivate Internet protocol (IP) addresses. Communicator 202 is configuredto translate the private identifiers into public identifiers, such aspublic IP addresses.

The private identifier may be an identifier used in a local area 101.The public identifier may be an identifier used externally. An exampleof a private identifier may be a local extension, such as 4512 and anexample of a public identifier may be a phone number such as 555-4512.Communicator 202 is configured to translate the private identifier to apublic identifier (e.g., public address, extensions with prefixes,etc.).

Central processing device 112 processes the request. For example,central processing device 112 may determine if the request is valid andeither accept or reject the request in a response.

Communicator 202 is configured to receive a response for a registerrequest from central processing device 112. The response is sent overWAN 110. The response may include contact information, which may includea username, public identifier, how long the registration is valid, etc.The username and public identifier may be for the telephone 106-1 thatsent the registration request.

The register request identifies telephone 106 to central processingdevice 112. The contact information for telephone 106 is then stored instorage device 204. Contact information is typically stored for theduration requested in the REGISTER request but gateway 102 may choose tostore the contact information for longer periods to handle lostconnections to central processing device 112. Thus, the contactinformation may then be used by gateway 102 to contact a telephone 106when connectivity to central processing device 112 is lost.

Communicator 202 then sends the response to telephone 106. As will bedescribed below, telephone 106 can then connect with destinationtelephones 106 after registering.

FIG. 3 depicts a message below for registering with central processingdevice 112 using a telephone 106 according to one embodiment of thepresent invention. At 302, telephone 106 sends a register request. Theregister request is received at gateway 102. Gateway 102 may then sendthe register request to central processing device 112 at 304.

In one embodiment, at 306, central processing device 112 may send anunauthorized message, such as a 401 Unauth message. This message mayindicate that the register request was an unauthorized register request.For example, central processing device 112 may require the registerrequest to be sent using credential information. This model eliminatesthe need for an intermediate device, such as gateway 102, to have thecredential information. The authentication information such as theusername and password is provisioned only on the telephone 106 andcentral processing device 112. Credential information may be anyinformation that is used to authenticate telephone 106, such as ausername, password, etc. If the register request does not include thisinformation and thus sends the unauthorized registration request messageto telephone 106 at 308.

Telephone 106 receives the message and sends a registration request withcredentials at 310. Gateway 102 forwards the registration request withcredentials to central processing device 112.

Central processing device 112 receives the registration request withcredentials and if the credentials are valid, may approve theregistration request. Central processing device 112 then stores thecontact information. If the registration is approved, at 314, aconfirmation message, such as a 200 OK message, may be sent. Gateway 102receives the message and forwards it to telephone 106 at 316. Thecontact information sent with the register request from telephone 106 isstored at gateway 102. If the authorized message is received at gateway102, then the contact information is stored at gateway 102. Because theauthorized message is received from central processing device 112,gateway 102 can assume that the telephone 106 is authorized.

FIG. 4 shows the message flow for routing communications between atelephone 106-1 and a telephone 106-2 according to one embodiment of thepresent invention. As shown, an INVITE message is sent from telephone106-1. The INVITE message is for a destination, such as telephone 106-2.Gateway 102 receives the INVITE message and forwards it to centralprocessing device 112 at 404.

Central processing device 112 may send an unauthorized registrationrequest message such as a 407 Unauth message, at 406. Gateway 102receives the unauthorized registration request message and sends anacknowledgement message, such as an ACK message, at 408. Gateway 102forwards the unauthorized registration request message to telephone 106at 410.

Telephone 106-1 sends an acknowledgement message (ACK) to gateway 102 at412. Because gateway 102 has already acknowledged receiving theunauthorized registration request message at 408, gateway 102 maysuppress the acknowledgement message received at 412.

At 414, telephone 106-1 sends an INVITE message with credentials.Gateway 102 receives the INVITE message and forwards the INVITE messagewith credentials to central processing device 112 at 416. When centralprocessing device 112 receives the INVITE message with credentials at416, central processing device 112 may look up information for telephone106-2 in its registrar contact table. Central processing device 112 thenplaces the call to an appropriate gateway 102 that handles telephonecommunications for telephone 106-2.

Assuming the credentials and the INVITE request are valid, centralprocessing device 112 sends an INVITE message to telephone 106-2 at 418.When the INVITE message is received at 418, gateway 102 may translate anexternal identity to a local identity in order to route the call totelephone 106-2. The information may be translated using the contactinformation stored in storage device 204. Gateway 102 receives theINVITE message for telephone 106-2 and forwards it to telephone 106-2 at420.

Telephone 106-2 sends a message indicating it is ringing at 422. Thismessage may be a 180 Ringing message. Gateway 102 receives the Ringingmessage and forwards it to central processing device 112 at 424. Centralprocessing device 112 then forwards a 180 Ringing message to telephone106-1 at 426, which is received at gateway 102. The Ring message is thenforwarded to telephone 106 at 428.

When telephone 106-2 is picked up, such as when the user answers thephone or voicemail picks up the message, a confirmation message, such asa 200 OK message, is sent from telephone 106-2 to central processingdevice 112 at 430. Gateway 102 receives the confirmation message, andmay translate the message from its local identifier to a publicidentifier. The message is then sent to central processing device 112 at432. Gateway 102 also sends an acknowledgement message to telephone106-2 at 434. Central processing device 112 also sends anacknowledgement message at 436 to gateway 102. Because gateway 102 hasalready sent an acknowledgement message at 434, the message that isreceived at 436 may be suppressed.

Central processing device 112 then sends a confirmation message, such asa 200 OK message to telephone 106. This message is intercepted atgateway 102. Gateway 102 forwards an acknowledgement message back tocentral processing device 112. Gateway 102 then forwards theconfirmation message at 442 to telephone 106-1. Telephone 106-1 may sendan acknowledgement message at 444 to gateway 102. Gateway 102 maysuppress this message.

After the above messaging scheme, telephone 106-1 may be connected totelephone 106-2. A communication session, such as a phone conversation,may then be performed between telephone 106-1 and telephone 106-2.

The above scheme of connecting a communication between telephone 106-1and telephone 106-2 may not be allowed if connectivity is lost betweengateway 102 and central processing device 112. FIG. 5 depicts a moredetailed block diagram of gateway 102 for handling communications whenconnectivity with central processing device 112 is lost according to oneembodiment of the present invention.

As shown, a connectivity detector 502 is configured to detect whenconnectivity to central processing device 112 is lost. For example,connectivity with central processing device 112 may be lost if aconnection through WAN 110 is lost, such as when a network connection isdown. Also, connectivity may be lost if central processing device 112 isnot functioning correctly. For example, central processing device 112may fail, be rebooted, etc.

Connectivity detector 502 is configured to use any techniques todetermine if connectivity is lost. For example, connectivity detector502 may ping central processing device 112 at certain intervals. Theping may involve sending messages that require responses from centralprocessing device 112. If a response is not received from centralprocessing device 112, connectivity detector 502 may determine thatconnectivity has been lost. In one embodiment, connectivity detector 502may use ICMP pings or SIP options requests to keep track of theconnectivity status.

If, at any point, connectivity detector 502 determines that connectivityis lost at central processing device 112 (denoted by the “X” in FIG. 5),connectivity detector 502 notifies communicator 202 that connectivityhas been lost. Communicator 202 is then configured to reroute calls whenconnectivity is lost such that they may not be routed to centralprocessing device 112.

In one embodiment, communicator 202 is able to route calls betweentelephones 106 that are found in local area 101. For example, whentelephone 106-1A sends an INVITE request for telephone 106-1B,communicator 202 may use the contact information received from centralprocessing device 112 during the registration to route the call betweentelephone 106-1A and telephone 106-1B. Because the contact informationis stored after an authorization message is received from centralprocessing device 112, communicator 202 can assume that if contactinformation is found in storage device 202 for both telephones 106-1Aand 106-1B, then communicator 202 is authorized to route thecommunication between telephone 106-1A and telephone 106-1B.

Checking if a telephone is authorized to initiate a communication isadvantageous because network security is still enforced. Centralprocessing device 112 normally routes communications and can authorizetelephones 106. However, without communicating with central processingdevice 112, gateway 102 may not know if a telephone is authorized. Thus,the storing authorization information from the registration process,gateway 102 may authenticate a telephone 106 that has registered.

As shown, then communicator 202 receives a request for connecting acommunication from telephone 106-1A for telephone 106-1B. The request isnot routed to central processing device 112. Rather, communicator 202looks up the contact information for telephone 106-1B in storage device204. If the contact information found in storage device 102, it mayindicate that the registration for telephone 106-1B is valid. Forexample, the contact information may have been authorized by centralprocessing device 112.

If the contact information is found, the communication is routed totelephone 106-1B using the contact information. The above processdescribed in FIG. 4 may be then performed with communicator 202 playingthe role of gateway 102 and central processing device 112 together. Forexample, this process will be described in more details in FIG. 6.

Accordingly, calls within a local area 101 may be enabled even ifconnectivity with central processing device 112 is lost. This is allowedbecause gateway 102 stores contact information during a registrationprocess for telephones 106. Gateway 102 also determines how long theregistrations are valid and only connects communications if centralprocessing device 112 determines that the registration requests fortelephones 106 are valid in one embodiment. Thus, the communications totelephones 106 in a local area 101 are sent only if they are authorizedby central processing device 112 according to one embodiment of thepresent invention. Accordingly, increased security is provided whencalls are not routed to central processing device 112.

FIG. 6 depicts a message flow when connectivity is lost with centralprocessing device 112 according to one embodiment of the presentinvention. As shown, at 602, telephone 106-1A sends an INVITE message togateway 102-1. Gateway 102-1, at 604, determines that central processingdevice 112 is not reachable. Gateway 102 then looks up contactinformation for telephone 106-1B in storage device 204. Gateway 102-1can then send the INVITE message to telephone 106-1B directly. This isbecause telephone 106-1B is in the same local area 101-1 as telephone106-1A.

Gateway 102-1 may also authenticate telephone 106-1A and/or 106-1B. Whenthe INVITE message at 608 is sent, the contact information is receivedfrom the INVITE message, gateway 102-1 may authenticate that telephone106-1B as authorized to receive communications. For example, gateway102-1 may check a local identity for telephone 106-1B, such as ausername, IP address, password, etc. In one embodiment, if gateway 102-1cannot verify usernames and passwords, gateway 102 may determine if theregistration stored in storage device 204 has become invalid. Forexample, gateway 102-1 may extend the registration duration fortelephones 106 such that they will expire during a bigger interval thanusual. This is because gateway 102 does not have the authenticationinformation. If the registration is still valid in storage device 204,then gateway 102-1 determines that telephone 106-1B is authorized toreceive communications.

In one embodiment, in order to ensure security is maintained, telephones106 may register before the connectivity is lost, and the registrationsmay be held for a certain duration. However, the telephones 106 may berequired to periodically renew their registrations. Also, whenconnectivity to a central processing device 112 is lost, no newregistrations may be accepted until the connectivity is restored.

Telephone 106-1B receives the INVITE message and sends a Ringingmessage, such as a 180 message, to gateway 102-1. Gateway 102-1 sendsthe 180 Ringing message to telephone 106-1A at 608.

When telephone 106-1B is picked up, a confirmation message, such as a200 OK message, is sent at 610. Gateway 102-1 receives the message andsends an acknowledgement message, such as an ACK message at 612.

At 614, gateway 102-1 sends a confirmation message, such as 200 OKmessage, to telephone 106-1A. Telephone 106-1A then sends anacknowledgement, such as an ACK message at 616. The telephone 106-1A andtelephone 106-1B may then be connected and a communication may takeplace, such as telephone conversation.

When connectivity detector 502 determines that connectivity has beenrestored, gateway 102-1 may resume sending communications throughcentral processing device 112.

Accordingly, embodiments of the present invention provide manyadvantages. For example, when connectivity to central processing device112 is lost, gateway 102 allows communications between telephones 106 ina local area 101 to continue. It is expected that LAN 104 may be morereliable than WAN 110, thus connectivity in LAN 104 may not be lost aseasily. Thus, calls within local area 101 may continue, even ifconnectivity with central processing device 112 is lost. In oneembodiment, telephones 106 may not be able to call external entities,such as calling from local area 101-1 to local area 101-2, but at leastthey may communicate with telephones 106 in the same local area.

The above is provided by storing contact information duringcommunications between telephones 106 and central processing device(s)112. This contact information may be stored after telephones have beenregistered and have been authorized. Thus, when communications areforwarded without contacting central processing device 112, security maybe maintain as communications may only be forwarded to telephones 106that have been authorized.

The present invention can be implemented in the form of control logic insoftware or hardware or a combination of both. The control logic may bestored in an information storage medium as a plurality of instructionsadapted to direct an information processing device to perform a set ofsteps disclosed in embodiments of the present invention. Based on thedisclosure and teachings provided herein, a person of ordinary skill inthe art will appreciate other ways and/or methods to implement thepresent invention.

The above description is illustrative but not restrictive. Manyvariations of the invention will become apparent to those skilled in theart upon review of the disclosure. The scope of the invention should,therefore, be determined not with reference to the above description,but instead should be determined with reference to the pending claimsalong with their full scope or equivalents.

1. A method for providing routing of calls when connectivity with acentral processing device is lost, the method comprising: receiving oneor more registration requests from one or more entities at a gateway;sending the one or more registration requests to the central processingdevice; receiving from the central processing device an authorizationmessage indicating that the one or more entities are registered with thecentral processing device; storing information for the one or moreentities at the gateway in response to the authorization message, theinformation including identification information for the one or moreentities and a duration for which registration of the one or moreentities is valid; receiving at the gateway a communication from a firstentity for a second entity in the one or more entities; and determiningwhether the first entity is authorized to initiate the communicationbased on the identification information and a validity of itsregistration; routing the communication to the second entity using theidentification information stored for the second entity when it isdetermined that the first entity is authorized to initiate thecommunication and that connectivity with the central processing deviceis lost, wherein the communication bypasses the central processingdevice.
 2. The method of claim 1, wherein the information includescredentials for the one or more users, wherein the gateway checks thecredentials to authenticate the first entity.
 3. The method of claim 2,wherein the credentials comprise a username and password.
 4. The methodof claim 2, wherein the communication includes a public identifier forthe second entity, wherein the gateway uses the identificationinformation to determine a local identifier for the second entity,wherein the communication is routed to the second entity using the localidentifier.
 5. The method of claim 1, wherein the first entity and thesecond entity are local to the gateway.
 6. The method of claim 1,wherein the gateway extends the duration for which the registration ofthe one or more entities is valid such that the information is storedduring the time.
 7. The method of claim 1, wherein determining theconnectivity with the central processing device is lost comprisespinging the central processing device.
 8. The method of claim 1, furthercomprising: determining that the connectivity with the centralprocessing device is restored; and routing communications from the oneor more entities to the central processing device.
 9. A gatewaycomprising a storage medium with control logic including a plurality ofinstructions configured to provide routing of calls when connectivitywith a central processing device is lost, the gateway comprising: logicconfigured to receive one or more registration requests from one or moreentities; logic configured to send the one or more registration requeststo the central processing device; logic configured to receive from thecentral processing device an authorization message indicating that theone or more entities are registered with the central processing device;logic configured to store information for the one or more entities atthe gateway in response to the authorization message, the informationincluding identification information for the one or more entities and aduration for which registration of the one or more entities is valid;logic configured to determine that the connectivity with the centralprocessing device is lost; logic configured to receive a communicationfrom a first entity for a second entity in the one or more entities;logic configured to determine whether the first entity is authorized toinitiate the communication based on the identification information and avalidity of its registration; and logic configured to route thecommunication to the second entity using the identification informationstored for the second entity when it is determined that the first entityis authorized to initiate the communication and that connectivity withthe central processing device is lost, wherein the communicationbypasses the central processing device.
 10. The gateway of claim 9,wherein the information includes credentials for the one or more users,wherein the gateway checks the credentials to authenticate the firstentity.
 11. The gateway of claim 10, wherein the credentials comprise ausername and password.
 12. The gateway of claim 10, wherein thecommunication includes a public identifier for the second entity,wherein the gateway uses the identification information to determine alocal identifier for the second entity, wherein the communication isrouted to the second entity using the local identifier.
 13. The gatewayof claim 9, wherein the first entity and the second entity are local tothe gateway.
 14. The gateway of claim 9, wherein the gateway extends theduration for which the registration of the one or more entities is validsuch that the information is stored during the time.
 15. The gateway ofclaim 9, wherein logic configured to determine the connectivity with thecentral processing device is lost comprises logic configured to ping thecentral processing device.
 16. The gateway of claim 9, furthercomprising: logic configured to determine that the connectivity with thecentral processing device is restored; and logic configured to routecommunications from the two or more entities to the central processingdevice.
 17. A system configured to provide routing of calls whenconnectivity with a central processing device is lost, the systemcomprising: a plurality of communication devices; a central processingdevice configured to process a communication from a first communicationdevice to a second communication device in the plurality ofcommunication devices; and a gateway comprising a storage medium with aplurality of instructions, including: logic configured to receiveregistration requests from first and second communication devices; logicconfigured to send the registration requests to the central processingdevice; logic configured to receive from the central processing devicean authorization message indicating that the one or more entities areregistered with the central processing device; logic configured to storeinformation for the first and second communication devices at thegateway in response to the authorization message, the informationincluding identification information for the one or more entities and aduration for which registration of the one or more entities is valid;logic configured to determine that the connectivity with the centralprocessing device is lost; logic configured to receive a communicationfrom the first communication device for the second communication device;logic configured to determine whether the first entity is authorized toinitiate the communication based on a validity of its registration; andlogic configured to route the communication to the second entity usingthe identification information stored for the second entity when it isdetermined that the first entity is authorized to initiate thecommunication and that connectivity with the central processing deviceis lost, wherein the communication bypasses the central processingdevice.
 18. The system of claim 17, wherein the central processingdevices comprises a Centrex.
 19. The system of claim 17, wherein thefirst and second communication devices comprise VoIP devices.